If a sausage fest is a party with too many guys, what do people call a party with too many girls?
Taco fiesta?
I dunno, I think a lot of people (read: guys) would call it a bonanza.
New York.
A hen party?
Although, that usually means only females.
I’ve always heard it called a tittie party or a baby shower. YMMV
SSG Schwartz
Oh, come on! Clam bake!
If they’re country girls, we could call it a “ho down”
I’ve also heard “taco party,” with all of its unappealing imagery.
A murder of vaginas, oh wait, that’s crows.
The classic “hen party” isn’t good enough?
Beat ya! 
An egg fest?
There’s no such thing as too many girls.
A keg of Slitz?
Oyster farm?
A mythology.
Depends on how much you like the girls who are present.
If they are your friends, you call it a “girl’s night!” and embrace it.
If you don’t like them, and/or don’t know them, it’s called a baby or wedding shower.
A buffet?
Vagaggle.
Utering.
Mammorama.
Tuna casserole?